1. Field of the Invention
The present invention relates to a method and apparatus for treating water to change washing or cleaning capability and surface activity of water by giving electric energy thereto.
2. Related Arts
A conventional method or apparatus for changing the quality of water uses first and second electrodes soaked in water, and the water is given energy by applying DC voltage between these electrodes. Such a method or apparatus is shown, for instance in Japanese Patents (Hei) 1-317592(A) and (Hei) 3-258392(A).
The former discloses a method of obtaining acidic water from an anode chamber separated by a membrane from a cathode chamber in an electrolytic cell, to kill Escherichia coli and other bacteria. The latter discloses a method of sterilizing water, which comprising steps of introducing water to be treated into cathode and anode chambers in an electrolytic cell, and adding a predetermined amount of a hypochlorite salt in the anode chamber until pH of the hypochlorite salt containing solution in the chamber becomes 3 to 7, to attain a relatively high sterilization effect with a relatively low chlorine remaining concentration.
In conventional water treating methods, one of the electrodes is used as one with positive polarity, whereas the other with negative polarity, and therefore, the electrodes are liable to be covered with deposited substance caused by the electrolysis after a while, thereby preventing transfer of electricity therebetween. For preventing the deposition on electrodes, there is a way to periodically change the polarity of DC voltage to be applied for the electrodes.
With recourse to the periodic change of polarity in DC voltage, however, a single water treating apparatus cannot be adjusted to meet requirements for different water treatments. Also, the periodic change of polarity in DC voltage necessitates an extra polarity reversing circuit for a constant voltage source and a low current circuit, and accordingly increasing cost of the apparatus.